Abstract
Typha angustifolia is a wetland macrophyte used in aquatic phytoremediation, yet the short-term physiological and molecular mechanisms underlying its responses to different heavy metals, and the potential modulatory role of carbon dots (CDs), remain insufficiently understood. In this study, we evaluated metal accumulation, biomass response, oxidative stress, and antioxidant defense after 48 h of exposure to Pb, Cd, Zn, Cr, Ni, and Cu, with or without CDs. Additionally, the early molecular response was assessed by quantifying the expression of two detoxification-related genes (PCS1 and HMA3) after 8 h of treatment. Metal accumulation occurred predominantly in roots, with Pb showing the highest root retention and Cr the lowest accumulation. High root bioconcentration factors and very low transfer factors, particularly for Pb and Cd (TF < 0.15), are consistent with a short-term phytostabilization-like response in T. angustifolia under acute exposure conditions. Metal exposure significantly reduced plant biomass, with Zn and Cu causing the strongest growth inhibition, whereas Pb and Cd had comparatively weaker effects under the tested conditions. Oxidative stress was evident from elevated malondialdehyde (MDA) levels and increased antioxidant enzyme activities, with Cd producing the strongest induction of CAT and POD, and Pb eliciting the highest SOD activity. RT-qPCR analysis further showed that metal stress significantly upregulated PCS1 and HMA3, especially in roots, where PCS1 reached a 6-fold increase and HMA3 a 4.5-fold increase relative to the control. Co-application of CDs attenuated these responses, reducing PCS1 expression from 6-fold to approximately 4-fold and HMA3 from 4.5-fold to 3.3-fold under high metal stress, consistent with a possible reduction in apparent detoxification demand under these conditions. In shoots, PCS1 and HMA3 were likewise reduced by CDs from nearly 6-fold to 4.4-fold and from 4.6-fold to 3.5-fold, respectively. These findings provide integrated short-term physiological and molecular evidence that T. angustifolia responds to heavy metal exposure through root-based retention, antioxidant activation, and detoxification-related pathways, while CDs attenuate stress-related molecular responses, particularly the induction of PCS1 and HMA3, under acute exposure conditions.